Core A (Trimer Production): Principal Investigator/Program Director: Klasse, PJ / Moore, John P. Abstract The goal of the Trimer Production Core is to support the work of the Research Projects by making appropriate quantities of high quality, cleaved, soluble envelope glycoprotein trimers and related reagents, and providing them to the Project Leaders and external collaborators. Dr. PJ Klasse will be Core Leader, with Mr. Albert Cupo directing the Core's activities on a day-to-day basis. The tasks of the Core are outlined below. Other responsibilities related to the production of trimers and other relevant antigens may arise during the life of the HIVRAD program and will be accomplished as and when appropriate. Aim 1: To produce milligram quantities of high quality SOSIP trimers and related Env proteins in mammalian cell lines by transient transfection. The Core will produce, in appropriate quantities, any trimers that are designed and evaluated (in small-scale production runs) by Project 1, and then selected for scale-up. The trimers will be assessed for purity and antigenic quality, in liaison with Project 1, and supplied to Projects 1 and 2 and collaborators. Aim 2: To create and use permanent cell lines expressing SOSIP.664 trimers. The Core will use now established methods to make stable CHO, 293T or 293S cell lines expressing wild type or epitope-tagged SOSIP.664 trimers based on various genotypes, under non-GMP conditions. Aim 3: To guide and facilitate the production and purification of SOSIP trimers under GMP conditions. A CMO (Catalent Inc.) will make large quantities of GMP-grade BG505 SOSIP.664 trimers under the direction of a consortium that also involves IAVI, BMGF and the Scripps CHAVI-ID. The Core will use its accumulated expertise to guide this process, including the creation and transfer of methods and the production of achievable quantities of reference standard trimers. By providing a central service to both Research Projects, and external collaborators, the Trimer Production Core will be intimately involved in the scientific program of the entire HIVRAD team.